In U.S. Pat. No. 3,297,663 (Herbst et al.) there is described a precipitation polymerization process for preparing polyvinyl phosphonic acid from vinyl phosphonic acid monomer dissolved in a non-polymerizable organic liquid that is a non-solvent for the polymer product. The polymerization is carried out with the use of a free radical polymerization catalyst and/or ultraviolet light. The Herbst et al. precipitation polymerization process is described as being unique in utilizing vinyl phosphonic acid monomer as the starting material and further in overcoming the difficulties encountered when polymerizing vinyl phosphonic acid dichloride (German Pat. No. 1,032,537) or vinyl phosphonic acid esters (Pudovik, Doklady. Akad. Nauk. 80, 65-68 (1951)).
The disclosures of Herbst et al. in column 1, line 20, to column 2, line 38, pertaining to prior art processes as well as the patented process are incorporated herein by reference.
U.S. Pat. No. 4,578,156 (Plazter) discloses and claims the use of polyvinyl phosphonic acid in preparing lithographic plates. More particularly, Plazter coats an anodized aluminum sheet with polyvinyl phosphonic acid and refers to prior U.S. Pat. No. 4,153,461.
The preparation of polyvinyl phosphonic acid is complicated even when employing the Herbst et al. precipitation polymerization process. Initially, this process involves a technically elaborate preparation of vinyl phosphonic acid (VPA) followed by the polymerization of the latter. It has been found, however, that this process gives many by-products that are carried into the final product. Consequently, the polyvinyl phosphonic acid product is characterized by varying random molecular weight distributions and varying solubilities in water at use concentrations. These are indications that undesirable by-products are produced and are carried into the PVPA product obtained by the Herbst et al. process.
Uniform PVPA is a must when it is to be employed in coating photolithography plates such as, for example, coating aluminum plates prior to application of the photosensitive layer. It is essential to seal the aluminum plate surface uniformly and with consistency so that uniform topcoat adhesion does not vary so that length of run and developing characteristics remain consistent.
It would be desirable to have a process available for the production of polyvinyl phosphonic from a monomer other than vinyl phosphonic acid, where substantially pure polyvinyl phosphonic acid with repeatable molecular weight distributions is obtained.